The invention relates to a method for adapting a mixture of a pilot control process for setting a fuel/air mixture for operating an internal combustion engine, wherein the pilot control process sets a fuel quantity as a function of an air quantity by means of an adaptable parameterized relationship.
When controlling the fuel/air ratio, the lambda value and the mixture for operating internal combustion engines it is customary to superimpose a closed-loop control process on a pilot control process. Furthermore, it is known to derive correction variables from the behavior of a closed-loop control variable in order to bring about incorrect adaptation of the pilot control process to changed operating conditions. This process is also referred to as adaptation of a mixture. U.S. Pat. No. 4,584,982 describes adaptation of a mixture with different adaptation variables in different ranges of the load rotational speed spectrum of an internal combustion engine. The different adaptation variables serve to correct different types of error. An error in the determination of the air mass flow rate acts multiplicatively on the metering of fuel. Influence of leakage air acts additively per time unit. An error during the compensation of switch-on delay of the injection valves acts additively per injection. These systematic errors are corrected by the mixture adaptation. The mixture deviations are adapted in the load/rotational speed range in which they have strong effects. Additive mixture deviations are adapted in the lower load/rotational speed range, and multiplicative deviations are adapted in the central load/rotational speed range. Calculated corrections are then used in the entire load/rotational speed range. According to legal specifications, errors which are relevant to exhaust gas are to be detected with on-board means and, if appropriate, an error lamp is to be activated. The adaptation of the mixture is also used for error detection. If correction intervention of the adaptation is strikingly large, this indicates an error.
EP 1382822 A2 discloses a method for adapting a fuel/air mixture in an internal combustion engine, in which various types of mixture deviations are adapted, in which during or after the adaptation of a first type of mixture deviation the influence of the first type of mixture deviation on an adaptation which has taken place beforehand of a second type of mixture deviation is estimated, and in which the adaptation of the second type of mixture deviation is corrected as a function of this estimate.
A disadvantage with the known methods for adapting a mixture is that for robust and rapid adaptation of a mixture said adaptation has to take place in two load/rotational speed ranges which are separate from one another. In particular, an intermediate range is necessary in which no adaptation takes place, in order to avoid oscillation of the adaptation between the adaptation values which correspond to the types of error. It is also disadvantageous that the known methods require regular operation in the lower load/rotational speed range since otherwise additive errors cannot be corrected. However, in motor vehicles with a hybrid drive operation of the internal combustion engine in the lower load/rotational speed range is avoided and is covered with an electric drive.
The object of the invention is therefore to make available a method for the improved and accelerated adaptation of a mixture for an internal combustion engine.